Laminated mounts consisting of a plurality of alternating layers of rubber and metal have been proposed for use in the primary suspension systems of railway vehicles as an alternative to leaf springs or coil springs. Properly designed, laminated mounts can be compact, dependable and provide controlled spring rates in several directions in a single mounting, in contrast to conventional coil and leaf springs. One of the primary design considerations for any mounting used in vehicle suspension systems is the provision of the proper ratio between the compression and shear spring rates. In many applications the compression spring rate must be such that adequate flexibility is provided in response to vertical motions for wheel load equalization in both the loaded and unloaded conditions of the vehicle. While the compression spring rate is necessarily relatively soft to achieve sufficient vertical flexibility, the shear spring rate must be stiff enough to provide stability to the vehicle in response to lateral (i.e., generally horizontal) movement.
Problems have been encountered in prior art laminated mounts with obtaining the appropriate compression to shear spring rate ratio. In those applications where space and load considerations require that vertical movements of the vehicle be accommodated by the mount in compression and lateral movements be accommodated in shear, it has been found that most prior art mounts provide a much higher shear springrate than desired to obtain the necessary compression springrate. The result is a mounting which is much stiffer and capable of less wheel load equalization that is required. One way of obtaining a softer compression spring rate has been to simply increase the number of elastomer layers in the laminated mount for greater total deflection under compression loads. However, this design results in a very soft shear springrate which is much lower than required. In addition, under compression loading such a mounting tends to be unstable which can further reduce the effective shear spring rate.